You have two choices, use a direct cable or use PhoneNet adapters. Given what you're trying to accomplish, either one will work so use whatever is more available in your area. While it is probably possible to build the cable, something tells me that it would be challenging given those tiny connectors.
I don't know if I'll change my challenge, but I might add to it. Looks like I might ALSO try to get an Atari TT030 running the Spectre GCR (Macintosh Emu up to 6.08). Trying to convince another Atari friend to enter the challenge to do the same.